At Japan's G7 summit, the big elephants are China and Russia

The longest shadows at the Group of Seven (G7) leaders' summit this week will be cast by two countries that weren't even invited to the Hiroshima gathering: China and Russia.

As the heads of the world's advanced democracies meet for three days from Friday in the western Japanese city, they will need to overcome some differences of their own, officials say, as they aim to project unity against challenges from Beijing and Moscow.

Divisions within the G7 appear to be the most notable over China, multiple officials told Reuters, with...